Conventional fiber optic cables include optical fibers which are capable of transmitting voice, video, and data information. A fiber optic cable should have a craft-friendly construction which permits ease of installation. Installation of a fiber optic cable typically requires the pulling of the cable through a cable passageway. The cable passageway can be, for example, a duct, a tube, a cable enclosure, building structural features, a trough, a tunnel, a tray, a trunk, a manhole, a handhole, a fingerhole, or a splice box.
The ease with which a fiber optic cable is installed in a cable passageway may be dependent on certain characteristics of the fiber optic cable. For example, surface area contact between the cable jacket, which is typically of the circular profile type, and surface areas in the cable passageway causes frictional resistance to the cable pulling force. Resistance to the cable pulling force can be a limiting factor regarding the length or ease of the cable to be pulled. Such resistance may also be a function of the coefficient of friction of the cable jacketing material. Additionally, a light-weight cable is generally easier to pull than a heavy cable. Cable flexibility is a factor as the use of stiff cable components makes the cable difficult to bend during the cable pulling operation. Cable size is also a factor as a cable with a small cross sectional area is generally easier to pull through a narrow passageway than a cable with a large cross sectional area. Moreover, apart from ease of installation, the cost per unit length of the cable may be an important factor in deciding between commercially available fiber optic cables.
Taking the foregoing factors into consideration, fiber optic cable designs having circular profile jackets are part of the background of the present invention. For example, a fiber optic cable which may be difficult to route through a passageway is disclosed in U.S. Pat. No. 5,029,974. The cable includes two steel strength members embedded in a circular profile cable jacket. The steel strength members are designed to resist axial compression due to, for example, aging shrinkage or thermal contraction of the cable jacket. The use of steel strength members creates a spark hazard and their weight may negatively affect the cable pulling operation. Additionally, the circular profile jacket can present a substantial degree of surface area contact and friction with the cable passageway that can result in substantial resistance to a cable pulling force.
Additionally, fiber optic cable designs having noncircular profile jackets may be difficult to install in cable passageways. For example, the cable disclosed in U.S. Pat. No. 4,844,575 is of the composite cable type and includes an oval profile cable jacket. The oval profile can present a substantial amount of surface area contact with the cable passageway, and the weight of the cable can make it difficult to install in a cable passageway.